Jump to content

Archived

This topic is now archived and is closed to further replies.

chionomaniac

Stratosphere Temperature Watch

Recommended Posts

Morning all

The ECMWF is keeping the theme of a major MMW this morning. If anything the temperature forecast seems to delay the cooling. The zonal winds are already negative at the 1hPa level and the temperatures are starting to rise as forecast.

post-4523-1232524049_thumb.png

post-4523-1232524045_thumb.png

I will hopefully have time to pick over the bones of it later. Though I did note that the 10hPa level zonal winds were a whopping -30m/s!

c

Share this post


Link to post
Share on other sites
me thinks its jus trying to make a pattern fit a time..seems ppl are saying the january 85 warming event was almost instant because it fitted the cold period..because 4-6 weeeks later didnt fit...take the major warming through dec 87..wat happened in jan/feb 88..ummm..nothing!!

Indeed you have a good point IMO. Why don't ALL SSW events lead to northern blocking and cold spells? Why do some lead quickly to blocking and some are lagged? IMO that is why I look for external forcing to come into play. Currently all I'll say is that I had a signal for latter third of Jan to be cold with blocking to NE extending to Greenland. This seems to be shown as potentially the case for end of Jan into early Feb. This could be reasonable however, I am not expecting a very cold Feb but a cold finale so really what i'm saying is that it may not happen at all.

BFTP

Share this post


Link to post
Share on other sites

Looking at the zonal wind profile we can see how the negative wind anomalies filter down to the troposphere towards the end of the forecast period.

Today

post-4523-1232531497_thumb.png

T+192

post-4523-1232531522_thumb.png

The negative wind anomalies seem to be forecast to affect the upper tropospheric layers at this time. I haven't really checked the models consistently but I would hope for a trend of high latitude pressure rises showing up soon at the far reaches of forecasting. Fingers crossed anyway.

c

Share this post


Link to post
Share on other sites
Guest North Sea Snow Convection
Morning all

The ECMWF is keeping the theme of a major MMW this morning. If anything the temperature forecast seems to delay the cooling. The zonal winds are already negative at the 1hPa level and the temperatures are starting to rise as forecast.

I will hopefully have time to pick over the bones of it later. Though I did note that the 10hPa level zonal winds were a whopping -30m/s!

c

Morning! - the 30hPa zonal winds also continue to suggest a comfortably easterly status too, and as you say, what is good is that high values appear to be being sustained after the main peak.

Regarding CM recent sceptical comments, I don't think anyone is trying to 'make' an event like this slot into a time. That would defeat the purpose of the thread, would it not? which is trying to analyse the progress of a winter stratospheric warming event, as one test case, in development and then see how if/when it manifests itself at the surface. That was one of the main intentions of the thread author in setting up this excellent thread.

It is indeed true that not all warming events are propagators, but most do at the least kick start a process which often carries through the second half of winter, when average stratospheric temp means, usually, start to recover from their winter lows anyway.

Of course many of us want this to be as fast as possible a tropospheric propagator, and lead to a bitter north easterly spell (and there is nothing wrong in that) but I think the debate on this thread is measured with lots of facts being brought to the table, at the same time as enjoying watching an exciting development unfold.

Looking at the zonal wind profile we can see how the negative wind anomalies filter down to the troposphere towards the end of the forecast period.

Today

The negative wind anomalies seem to be forecast to affect the upper tropospheric layers at this time. I haven't really checked the models consistently but I would hope for a trend of high latitude pressure rises showing up soon at the far reaches of forecasting. Fingers crossed anyway.

c

I would agree with that too :rolleyes:

Share this post


Link to post
Share on other sites

It will be a forgone conclusion that once the wave propergates downwards- between 16-23 days the preponderance of Blocking at high lattitudes could become significant, of course it could happen a little sooner my the mere fact of the Vortex being Split-

The critical part for the UK is how far South the major (polar) Easterly Trade anomaly sits - It 'could' just sit with a huge Easterly shear at 60N-

This would look like a String of High Pressure Belts over Northern Russia, Canada & Greenland with an epic long fetch of reverse zonality & cold air stretching across the Northern Climbs, however 60N as a convergence zone is no good-

We need A weakened vortex & Strong Polar cell + a weakened Ferrel Cell- giving a Convergence zone along 50N

FEB 4-6 is my key Dates ( Hopefully then the Easterly trades around the base of the Azores high will have broken by then -)

S

Share this post


Link to post
Share on other sites
Guest North Sea Snow Convection
We need A weakened vortex & Strong Polar cell + a weakened Ferrel Cell- giving a Convergence zone along 50N

FEB 4-6 is my key Dates ( Hopefully then the Easterly trades around the base of the Azores high will have broken by then -)

S

GP has referred to this in recent days as the last of the dominoes to topple in order to get into a sustained cold spell. Signs are reasonable that the Azores High will take a hike in the extended period.

Share this post


Link to post
Share on other sites
Guest Mike W

I was just wondering how long does it take for Stratosphere Warming to influence our UK weather becasue it's interesting that the SW we got starting last winter and then we had that southerly jet summer later on and was wondering if the SW from the winter was at least part of the reason behind us getting that around avergae summer temps, did the same happen in 2007 with SW? I may well be massively wrong as I'm not a expert or anything like one. What I'm wondering really is that is it a case that SW takes several months to influence our UK weather and not a matter of weeks , so I was wondering if this was the case would we then need SW to happen noticeably in the summer or autumn or both to give the much wanted winter synoptics [not by me].

Share this post


Link to post
Share on other sites

The effect on synoptics takes around 20 days as Steve says, thus we should expect decent blocking to the north within the first ten days of February.

Share this post


Link to post
Share on other sites
It will be a forgone conclusion that once the wave propergates downwards- between 16-23 days the preponderance of Blocking at high lattitudes could become significant, of course it could happen a little sooner my the mere fact of the Vortex being Split-

The critical part for the UK is how far South the major (polar) Easterly Trade anomaly sits - It 'could' just sit with a huge Easterly shear at 60N-

This would look like a String of High Pressure Belts over Northern Russia, Canada & Greenland with an epic long fetch of reverse zonality & cold air stretching across the Northern Climbs, however 60N as a convergence zone is no good-

We need A weakened vortex & Strong Polar cell + a weakened Ferrel Cell- giving a Convergence zone along 50N

FEB 4-6 is my key Dates ( Hopefully then the Easterly trades around the base of the Azores high will have broken by then -)

S

I would certainly agree with SM here. As ever, it takes a number of different factors to come together for us to have an increased risk of cold. The forecast vortex split occurs, leaving an area north of us that I reckon will be conducive for tropospheric high pressure formation, even before the full propagation occurs. The following chart at T+240 from the lowest reaches of the stratosphere shows us just where an artic high could manifest itself north of us, even before the main event occurs. So I think from now it will be worth looking out into FI for signs that this could occur.

post-4523-1232545767.gif

c

EDIT Just seen GP's post on GWO thread and he is suggesting exactly the same so that is good.

Share this post


Link to post
Share on other sites

Big Steve's point is really what I'm getting at...it may not happen as it stays too far north...that would be the most frustrating set up imaginable for cold lovers. IMO if this is to happen it will be a quicker event rather than slow...so Steve's dates max or slightly before I'm looking at.

What is favourable IS that the external forcing suggests and shows that the jet is kicked south.

BFTP

Share this post


Link to post
Share on other sites

Latest progress on the warming up phase of the SSW. The following charts, that get updated weekly, show that the warming is well under way even right down to the 70 hPa level. I am expecting the warming at the 10 hPa level to go off the edge of the chart if the forecast is anything to go by. So far, so good.

post-4523-1232568004_thumb.png

post-4523-1232568020_thumb.png

post-4523-1232568031_thumb.png

Good to today that the first tentative signs of polar height rises are occurring in FI on some models. It will be good to watch how this will be modeled and hopefully come to fruition in the coming weeks.

c

Share this post


Link to post
Share on other sites
Big Steve's point is really what I'm getting at...it may not happen as it stays too far north...that would be the most frustrating set up imaginable for cold lovers. IMO if this is to happen it will be a quicker event rather than slow...so Steve's dates max or slightly before I'm looking at.

What is favourable IS that the external forcing suggests and shows that the jet is kicked south.

BFTP

What can be observed on the 500hpa charts is that the upper tropospheric vortex doesn't really 'split' as such; but we have a warming out of the upper trough over eastern Siberia; with the core filling slightly as heights develop in a band along the subpoles across north of Russia towards eastern Greenland. Meanwhile; the 2nd gyre of the tropospheric vortex shows signs of slight weakening post T144 on the GFS; albeit plenty of low heights into Northern Canada and Arctic west of Greenland.

Hard to tell really how extensive this easterly anamalous flow at 60N will be; the spatial extent of the warming over the stratosphere and whether this is going to impede a conducive poleward amplification of the jet east of the troffing near America\Canada to make height rises beneficial for us in the UK. Just too far out and speculative to say at the moment. We may just end up in a col as things just stall for a while...a southward moving jet is just part of the picture as we know.

Share this post


Link to post
Share on other sites

This may be nothing but i ran through the historical El Nino/ La Nina episodes (1950 to present) and then compared them to the zonal temperature anomaly time series when there was stratospheric warmings in the winter months to see if there was any correlation as to why some warmings have more of an impact than others.

I then checked the warming against the archive anomaly synoptics to see what impact the warmings had and it appears any year when there was a El Nino there was little impact as far as blocking highs to the north or cold weather pattern over Europe and the UK.

During La Nina or neutral conditions there was more of an impact. This could all be coincidence or to do with other teleconnections ie PDO, QBO,PNA strength of warming etc,etc but i thought i would put it on here to see what others thought.

Share this post


Link to post
Share on other sites
Guest North Sea Snow Convection
Latest progress on the warming up phase of the SSW. The following charts, that get updated weekly, show that the warming is well under way even right down to the 70 hPa level. I am expecting the warming at the 10 hPa level to go off the edge of the chart if the forecast is anything to go by. So far, so good.

Good to today that the first tentative signs of polar height rises are occurring in FI on some models. It will be good to watch how this will be modeled and hopefully come to fruition in the coming weeks.

c

Virtually instant propagation already. Last winter saw an initial sharp rise at 10hPa and a very slight adjustment towards average on the 30hPa over a period of time. This one is poised to already overtake that in terms of penetration on the first/second day :)

Interesting thoughts tundra - lots to investigate!

Share this post


Link to post
Share on other sites

The stratospheric warming is still on track and still forecast to be unprecedented.

The mean zonal winds at the 10 and 30 hPa levels are still forecast to be negative by record amounts. How this transfer downwards towards the troposphere remains to be seen.

post-4523-1232614323_thumb.png

post-4523-1232614306_thumb.png

These negative anomalies have now reached the 50hPa level so that indicates that good propagation is occurring

post-4523-1232614478_thumb.png

The wind anomalies are in fact forecast to filter right down into the troposphere. If this was to occur then I dare say there will be big changes on the models very soon. After all the following is forecast for T+192 and would affect the troposphere.

post-4523-1232615180_thumb.png

c

Share this post


Link to post
Share on other sites
Guest North Sea Snow Convection

I used the impact of a freight train analagy last night in the model thread and it was exactly those wind anomalies arriving at the surface that I had in mind when suggesting sudden changes on the model output ahead

Share this post


Link to post
Share on other sites
I used the impact of a freight train analagy last night in the model thread and it was exactly those wind anomalies arriving at the surface that I had in mind when suggesting sudden changes on the model output ahead

Yes I saw that. And as we have not seen a MMW as strong as this before and that shows such (forecast) propagation it really is an unknown of how this might affect us . But I have my suspicions. Keep those quality posts coming.

Share this post


Link to post
Share on other sites
After all the following is forecast for T+192 and would affect the troposphere.

In other words FI on the tropospheric models. Should T+192 be considered FI on the stratos models, or is the output generally more accurate to a longer range?

Yes I saw that. And as we have not seen a MMW as strong as this before and that shows such (forecast) propagation it really is an unknown of how this might affect us . But I have my suspicions. Keep those quality posts coming.

I wonder!

Share this post


Link to post
Share on other sites
In other words FI on the tropospheric models. Should T+192 be considered FI on the stratos models, or is the output generally more accurate to a longer range?

I wonder!

I wonder indeed!

The stratospheric forecasts have verified well except for 1 blip a couple of weeks ago when the ECM was unsure over the start of the MMW. Generally there is less in the stratosphere for interactions to occur ( such as seas, land masses, mountain ranges Etc) so forecasts can be more reliable.

Share this post


Link to post
Share on other sites
Guest North Sea Snow Convection
In other words FI on the tropospheric models. Should T+192 be considered FI on the stratos models, or is the output generally more accurate to a longer range?

I wonder!

I would suggest that the stratospheric forecasts, especially from ECM, are more reliable. They are not bullet proof, nothing is, but the strength of this MMW has actually increased with time and not the other way around. The peak intensities have been forecasted consisitently for several days now. It is now underway, and still predicted, as chionomaniac says, to be a fairly unprecedented strength. We we have to see how or whether that intensity is matched, or occurs, on the ground...Like chionomaniac also, I have my personal suspicions :lol:

Edit as above! - (great minds..or fools?? :lol: )

Share this post


Link to post
Share on other sites
I would suggest that the stratospheric forecasts, especially from ECM, are more reliable. They are not bullet proof, nothing is, but the strength of this MMW has actually increased with time and not the other way around. The peak intensities have been forecasted consisitently for several days now. It is now underway, and still predicted, as chionomaniac says, to be a fairly unprecedented strength. We we have to see how or whether that intensity is matched, or occurs, on the ground...Like chionomaniac also, I have my personal suspicions :lol:

Edit as above! - (great minds..or fools?? :lol: )

does all this mean it will get colder here in uk mid feb? :lol:

Share this post


Link to post
Share on other sites
Guest North Sea Snow Convection
does all this mean it will get colder here in uk mid feb? :lol:

If we can get the right convergence zone for cold air far enough south - there is every possibility :lol:

Share this post


Link to post
Share on other sites
This may be nothing but i ran through the historical El Nino/ La Nina episodes (1950 to present) and then compared them to the zonal temperature anomaly time series when there was stratospheric warmings in the winter months to see if there was any correlation as to why some warmings have more of an impact than others.

I then checked the warming against the archive anomaly synoptics to see what impact the warmings had and it appears any year when there was a El Nino there was little impact as far as blocking highs to the north or cold weather pattern over Europe and the UK.

During La Nina or neutral conditions there was more of an impact. This could all be coincidence or to do with other teleconnections ie PDO, QBO,PNA strength of warming etc,etc but i thought i would put it on here to see what others thought.

The conditions which set off a stratospheric warming or disturbance or the vortex include persistent anticyclones and rossby wave breaking. Since la nina relates to strong trades and a fixed pattern of anticyclines either side of the date in the pacific then this would possibly provide a strong trigger for the stratospheric disturbance.

If you had analysed the QBO though you may have come to different conclusions so the splitting is rather unusual compared to recent years for this time of year. The details at the moment from the stratospheric forecast are not quite working out for a cold spell in the UK, but it does look like a cross polar flow may start up. What I would point to is some pretty unusual weather across the US.

ECM deterministic forecast is not that encouraging though at the minute for UK snow or for tropospheric weather to reflect conditions in the stratosphere. We wait and see how it develops as there would appear to be good indications for north atlantic ridging despite what the models show.

Share this post


Link to post
Share on other sites
Guest North Sea Snow Convection
The conditions which set off a stratospheric warming or disturbance or the vortex include persistent anticyclones and rossby wave breaking. Since la nina relates to strong trades and a fixed pattern of anticyclines either side of the date in the pacific then this would possibly provide a strong trigger for the stratospheric disturbance.

If you had analysed the QBO though you may have come to different conclusions so the splitting is rather unusual compared to recent years for this time of year. The details at the moment from the stratospheric forecast are not quite working out for a cold spell in the UK, but it does look like a cross polar flow may start up. What I would point to is some pretty unusual weather across the US.

ECM deterministic forecast is not that encouraging though at the minute for UK snow or for tropospheric weather to reflect conditions in the stratosphere. We wait and see how it develops as there would appear to be good indications for north atlantic ridging despite what the models show.

In terms of the life span of a warming event such as this though, these forecasts are very short term. I don't think that any real tropospheric effects beyond the splitting of the vortex are anticipated before or by the end of the month anyway.

Share this post


Link to post
Share on other sites

10hPa warming close to record levels already

post-4523-1232639553_thumb.png

c

Share this post


Link to post
Share on other sites

×
×
  • Create New...